Recently, imaging elements are getting more widely used, not only in mobile apparatuses such as digital cameras and mobile phones, but also in monitoring apparatuses and onboard apparatuses. Besides, IC chips including imaging elements are getting to have larger number of pixels. Under such circumstances, semiconductor devices (packages) are required to have high packaging accuracy and high packaging reliability as well as to be small and light.
An example of semiconductor devices including imaging elements is a package for an optical semiconductor element disclosed in Japanese Unexamined Patent Publication No. 33407/2002 (Tokukai 2002-33407; published on Jan. 31, 2002). The following shortly explains a structure of a conventional semiconductor device with reference to FIG. 5. FIG. 5 is a cross sectional drawing for illustrating a structure of a conventional semiconductor device 40.
In the semiconductor device 40, an IC chip 44 having an optical function, such as an imaging element, is bonded with a substrate 41 via a die-bonding member 43. A wire 45 extends from an electrode pad 44a of the IC chip 44, and is electrically connected with an externally connecting terminal 47 via an electrode pad 41a of the substrate 41.
Further, because the IC chip 44 includes an optical element such as an imaging element, a lid member 46 including a glass window which transmits light is provided above the IC chip 44. This package is connected with a mounting substrate 48 via the externally connecting terminal 47 made of solder or the like.
However, the conventional structure as explained above has the following problems.
In a semiconductor device which includes a ceramic substrate and in which an IC chip package or similar package is bonded with a mounting substrate, when a temperature around the semiconductor device changes, a stress occurs due to a difference in coefficient of thermal expansion between the ceramic substrate and the mounting substrate. At that time, if the semiconductor device includes a bonding section made of a bonding material, particularly solder, then the stress is applied on the bonding section in the semiconductor device. Consequently, the bonding section may be broken.
Further, in a case where the semiconductor device is used as a member of an apparatus, an external stress or a stress due to shock caused by falling of the apparatus may cause cracks in the bonding section. Consequently, defective electric connection may occur.
As described above, the conventional semiconductor device does not have enough packaging reliability. Therefore, if the semiconductor device is used in an apparatus which may be shocked or which may be placed under circumstances with a great change in temperature, then problems may occur.
Further, in a packaging structure using conventional solder, if packaging height is required to be large for increasing packaging reliability, then it is necessary to increase the amount of solder.
However, with the method, when solder is melted on the mounting substrate, the shape of the solder changes. Therefore, as the amount of solder becomes larger, it gets more and more difficult to control the shape of solder. Consequently, as the amount of solder becomes larger, positional accuracy or height accuracy drops in packaging. Further, packaging reliability is not expected to increase greatly.